The high-pitched whistling or squealing sound sometimes produced by a hearing aid is known as acoustic feedback. This noise is one of the most common and frustrating issues for users, but it is rarely a sign of a broken device. The squeal is a predictable physical reaction that occurs when amplified sound escapes the ear canal and is immediately picked up by the device’s microphone. Understanding this process is the first step toward finding a simple solution.
The Mechanism of Acoustic Feedback
The sound is produced when an amplified sound wave, intended to travel deep into the ear canal, leaks out of the ear. The hearing aid’s microphone, positioned on the outside of the device, captures this escaping sound and sends it back to the amplifier. The system re-amplifies this sound and sends it back to the speaker, creating a continuous, rapid cycle known as a feedback loop.
This looping effect happens almost instantaneously, resulting in the characteristic high-frequency whistle. Modern hearing aids are equipped with sophisticated feedback suppression systems that use digital signal processing to identify and cancel out this runaway sound. However, even advanced technology can be overwhelmed if too much amplified sound escapes the ear.
Physical Causes of Sound Leakage
The most frequent cause of squealing is a physical breach in the seal between the hearing aid and the ear canal. The device must fit snugly to prevent sound from escaping the ear and returning to the microphone. An improperly inserted hearing aid, where the dome or earmold is not seated deeply or correctly, leaves a gap that allows sound to leak out.
Changes in the shape of the ear canal can also compromise a previously good fit. Natural movements, such as chewing, talking, or yawning, can temporarily shift the ear canal’s shape and break the seal, causing momentary feedback. Weight changes, aging, or surgery can alter the ear’s anatomy, making a custom-fit earmold or dome loose over time.
A significant buildup of earwax is another common culprit. When sound waves leave the hearing aid, they hit the earwax blockage, which reflects the sound back toward the device’s microphone. This reflected sound initiates the feedback loop and causes the device to squeal.
Device Factors Contributing to Squealing
Beyond issues related to physical fit, the device’s settings and condition can directly contribute to feedback. Setting the hearing aid volume too high increases the amount of amplified sound pressure in the ear canal. If this over-amplification exceeds the threshold the device’s seal can contain, the excess acoustic energy will escape and initiate the squealing.
The design of the device’s venting system is also a factor, particularly in custom earmolds. Vents are small channels that allow air to pass through the earmold to relieve pressure. If a vent is too large, however, it can also act as an escape route for amplified sound. Physical damage to the hearing aid, such as a crack in the casing, a tear in the tubing, or a worn-out dome, can also create a pathway for sound leakage.
Practical Steps to Eliminate Hearing Aid Squeal
The first action is to check the hearing aid’s placement and ensure the dome or earmold is fully inserted into the ear canal. Gently remove the device and reinsert it, making sure it sits snugly without any gaps. If the squealing only occurs when the volume is turned up, try lowering the setting slightly to see if the feedback stops.
Regularly inspecting the ear canal for earwax buildup is a helpful preventative measure. If an accumulation is visible, it should be removed by a professional, as pushing wax deeper with a cotton swab can worsen the problem. Also, check the hearing aid’s tubing and domes for signs of wear, hardening, or tears, which may indicate a need for replacement.
If these steps do not resolve the feedback, consult an audiologist for a professional assessment. They can inspect the ear for blockages, check the device for internal component failure, and run the built-in feedback cancellation program. In some cases, a new, better-fitting dome or a newly molded earmold may be necessary to restore a proper seal.